In certain known wind turbines, the rotating electric machine frame serves to: transmit the forces and moments generated on the rotating machine to the main frame of the wind turbine; prevent excessive vibration of the rotating machine; and support the rotor and possibly also the blade assembly.
Wind turbine rotating electric machines, particularly those used on large wind turbines, must have special characteristics, as compared with ordinary rotating electric machines. For example, they must be relatively lightweight, must be relatively easily accessible for maintenance, and their component parts must be relatively easy to assemble and disassemble, both when installing and repairing the machine. Moreover, the rotating electric machine must be connectable relatively easily to the main frame and the blade assembly, and must be so designed as not to require excessively large, heavy main frames.
In wind turbine technology, the trend is towards increasingly powerful (i.e., increasingly large-diameter) rotating electric machines. At the same time, a relatively small air gap is required to achieve optimum efficiency of the machine. The difficulty of producing rotating electric machines with a radially small, circumferentially constant air gap therefore increases alongside an increase in the diameter of the machine.